How can I stop Blender from selecting vertices on backfaces?
The closest thing would be to select one vertex of a backface and select similar vertices Shift-G Normal adjust the threshold in the last operator panel (Left to the viewport if not visible toggle with T)



and hide the selection H, after editing unhide Alt-H.

Note: Hiding backfaces would only prevent Blender from filling them, all vertices,edges will still be selectable in Edit Mode: